Grinding, polishing, and cutting wheels are used in a variety of industrial processes. Such wheels generally comprise a matrix of abrasive particles forming a working surface around an outer peripheral surface of the wheel. In use, such wheels are rotated and placed in contact with a part which is to be ground, polished or cut. During use such wheels can be deformed from their original wheel profile, become glazed due to rounding of the abrasive grains at the working surface of the wheel, or become loaded with contaminant material. Dressing a wheel is intended to remove portions of the working surface of the wheel in order to return the wheel to its original profile, dislodge rounded abrasive grains to expose fresh grains, and/or clean contaminant material from the wheel. This is achieved by rotating the wheel and moving a wheel dresser tool across the working surface of the wheel.
FIG. 1 illustrates the process of wheel dressing. A wheel 2 having a working surface 4 is rotated in a direction R. A dresser tool 6 comprising a dresser work piece 8 in a holder 10 is applied to the working surface of the wheel and moved backwards and forwards across the working surface of the wheel in a direction X which is perpendicular to the direction of rotation or the working surface of the wheel at the point of contact and parallel to the axis of rotation of the wheel. Material is removed from the working surface of the wheel to regain a good working surface such that the working lifetime of the wheel can be extended.
Diamond material has been found to be useful for the fabrication of dresser tools due to its extreme hardness and wear resistance. Such diamond dresser tools generally comprise a diamond work piece mounted in a holder which may be fabricated, for example, using a metal material. The diamond work piece may be fabricating using a single crystal of natural, CVD synthetic, or HPHT synthetic diamond material. Alternatively, the diamond work piece may comprise a plurality of diamond grains bounded in a matrix of binder material. Alternatively still, the diamond work piece may be fabricating using polycrystalline CVD synthetic diamond material which comprises a plurality of diamond grains directly bonded together via diamond-to-diamond bonding as a result of the CVD growth method.
The present invention relates specifically to diamond dresser tools in which the diamond work piece of the tool is formed of a polycrystalline CVD diamond work piece. Such polycrystalline CVD synthetic diamond dressers are fabricated as illustrated in FIG. 2. First, a free-standing disk of polycrystalline CVD diamond material 20 is fabricated using for example, a microwave plasma activated CVD diamond synthesis technique. A plurality of dresser logs 22 can then be laser cut from the disk of polycrystalline CVD diamond material 20 (only one dresser log 22 is illustrated for clarity). The dresser logs 22 have a working surface 24. The dresser logs are mounted in a holder 26 with the working surface 24 exposed for dressing applications. During use the working surface 24 is applied to a working surface of a wheel as illustrated in FIG. 1. Over time the working surface 24 is worn away and the dresser log gradually gets shorter along a length l as illustrated in FIG. 2 until it is completely worn back and a new tool is needed.
It is an aim of embodiments of the present invention to decrease the wear rate of polycrystalline CVD synthetic diamond dresser parts thereby increasing their lifetime in use.